The fungus Paecilomyces lilacinus (image) produces leucinostatins, which are peptaibiotics that exert a range of biological activities, including antimalarial, antiviral, antitumor, and phytotoxic activities. In an article published online on September 3, 2014 in The Journal of Antibiotics, Dr. Ana Martinez and Dr. Luiz Moraes, of the University of Sao Paulo in Brazil, report the development of an analytic method utilizing LC-MS/MS in the precurson ion and product ion modes to identify five new leucinostatins from this fungus. The scientists used Direct Infusion-MS (DI-MS) to help identify the most abundant leucinostatins (F, D, B2, S, A, and K). They noted that MS/MS analysis using a triple quadrupole operating at different scan modes is a versatile tool with which to study natural products, especially peptaibiotics. They commented that although DI-MS full-scan analysis is both rapid and sensitive, it cannot distinguish between peptide isomers. On the other hand, although LC-MS/MS operated in the precursor ion and product ion modes is time-consuming, it does allow the identification of the structures of isomers or isobars in a crude extract. [The Journal of Antibiotics abstract]
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